1. Field of the Invention
This invention relates to a developing liquid recovery device for use in a copying machine. More particularly, it relates to a carrier liquid recovery device for use in an electrophotographic copying machine of the wet development type.
2. Description of the Prior Art
In an electrophotographic copying machine of the wet development type, it has usually been the practice to form an electrostatic latent image on a photosensitive sheet or medium as by applying of electrostatic charge and image light, directing the image-bearing sheet or medium into a pool of developing liquid composed of carrier liquid such as Isopar or like petroleum with toner dispersed therein to develop the latent image into a visible image. Where a photosensitive sheet is used, most of the developing liquid remaining thereon is then squeezed by a pair of squeeze rollers, whereafter any residual carrier liquid on the photosensitive sheet is vaporized by a fixing-drying device to fix the toner on the sheet. In case of an image transfer type copier, the toner image on the photosensitive medium is transferred to transfer medium through the agency of carrier liquid, and such transfer medium is further passed to a fixing-drying device, where the residual carrier liquid is vaporized to fix the toner image.
The carrier vapor produced in the above case is usually exhausted from the machine directly into the atomospher such as office room or the like, but even a slight amount of carrier liquid should not be neglected because it is a hygienically deleterious petroleum solvent. Especially, if a copying machine were installed in a shut-up room, the carrier vapor exhausted from the machine at a high rate per unit time would harm the health of the workers in the room inasmuch as the rate of exhaust in newer machines has a tendency toward further increase with the increasing copying speed.
Also, the amount of the carrier liquid carried away with the photosensitive sheet or the transfer sheet from the developing device is inappreciable when taken with respect to an individual sheet (0.3 to 1 cc per sheet of format A), whereas mass production of copies would involve a considerable waste of carrier liquid which should never be neglected from an economical point of view.
Recovery of carrier vapor by utilizing the adsorbing property of active carbon or by condensing the vapor has heretofore been proposed, but it is nearly impossible to attain sufficient recovery of carrier vapor by these means.
Recovery of carrier vapor by cooling and condensing the vapor has also been proposed. However, the recovered carrier liquid is heated to a high temperature in the fixing station to dry and fix the copy medium. As a result, part of the carrier liquid is thermally cracked and activated, thus producing a considerably unpleasant odor. If such odorous carrier liquid were returned to the developing liquid for repeated use, the odor would remain on copy mediums even after they have passed through the fixing-drying device, and such residual odor would finally be exhausted with copy mediums to cause unpleasant conditions for the workers in the room, although the odor might be slight in extent.